DE112021005267T5 - SELF-ADHESIVE LAYER - Google Patents

Abstract

A pressure-sensitive adhesive sheet is provided which has moderate pressure-sensitive adhesive properties to an encapsulation resin for encapsulating a semiconductor chip therein and the semiconductor chip, can be easily detached from the encapsulation resin, hardly causes an adhesive residue when it is detached, and hardly causes a step between the semiconductor chip and the encapsulation resin after it is detached. The pressure-sensitive adhesive sheet of the present invention comprises: a base material; and a pressure-sensitive adhesive layer disposed on at least one side of the base material, the pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive layer having a sinking amount of 5 µm or less measured with a TMA in an environment at 23 °C, and wherein an S component obtained by pulse NMR of the pressure-sensitive adhesive layer has a T2 relaxation time (T2s) of 45 µs or less.

Description

technical field

The present invention relates to a pressure-sensitive adhesive sheet.

State of the art

In recent years, in the manufacture of a semiconductor device including a semiconductor chip, the semiconductor chip has sometimes been encapsulated in a resin in order to, for example, prevent failure of the semiconductor chip and expand a metal wiring. In the resin encapsulating step, the semiconductor chip is encapsulated in the resin on a pressure-sensitive adhesive sheet in view of, for example, workability. For example, in order to prevent movement of the semiconductor chip, the plurality of semiconductor chips are placed on the pressure-sensitive adhesive sheet serving as a predetermined temporary fixing material, and the semiconductor chips are encapsulated together on the pressure-sensitive adhesive sheet. Thereafter, in a predetermined subsequent step, the pressure-sensitive adhesive layer is separated from the resin in which the semiconductor chips are encapsulated.

The use of a known pressure-sensitive adhesive sheet in such a step as described above has a problem that adhesive residue occurs in a structural body including the encapsulating resin and the semiconductor chips when the pressure-sensitive adhesive sheet is peeled off from the structural body. In addition, pressing the semiconductor chips into the pressure-sensitive adhesive sheet when encapsulating them leads to a problem that a step occurs between each of the semiconductor chips and the encapsulating resin. Such a stage causes the protection of the semiconductor chips to become insufficient and is responsible for, for example, the inadequacy described below that a metal wiring cannot be formed. In addition, an adhesive residue resulting from the step is likely to occur.

document list

patent documents

• [PTL 1] JP 2001-308116 A
• [PTL 2] JP 2001-313350 A

Summary of the Invention

Technical problem

The present invention was made to solve the above problems of the prior art, and an object of the present invention is to provide a pressure-sensitive adhesive sheet that has moderate pressure-sensitive adhesive properties to an encapsulating resin for encapsulating a semiconductor chip therein and a semiconductor chip can be easily detached from the encapsulating resin , scarcely causes adhesive residue upon peeling them off, and scarcely causes step between the semiconductor chip and the encapsulating resin after peeling them off.

the solution of the problem

According to one embodiment of the present invention, there is provided a pressure-sensitive adhesive sheet comprising: a base material; and a pressure-sensitive adhesive layer disposed on at least one side of the base material, the pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive layer having an amount of sink of 5 µm or less measured with a TMA in an environment at 23 °C, and wherein an S component obtained by pulse NMR of the pressure-sensitive adhesive layer has a T ₂ relaxation time (T _2s ) of 45 µs or less.

In one embodiment, after dropping 4-tert-butylphenyl glycidyl ether onto a surface of the pressure-sensitive adhesive layer and allowing the pressure-sensitive adhesive layer to stand for 1 minute, the thickness of the pressure-sensitive adhesive layer changes at a ratio of 160% or less.

In one embodiment, after dropping 4-tert-butylphenyl glycidyl ether onto a surface of the pressure-sensitive adhesive layer and allowing the pressure-sensitive adhesive layer to stand for 1 minute, the thickness of the pressure-sensitive adhesive layer changes to an extent of 20 μm or less.

In one embodiment, the pressure-sensitive adhesive layer includes a pressure-sensitive adhesive and the pressure-sensitive adhesive includes a base polymer having an sp value of from 18 (cal/cm ³ ) ^1/2 to 20 (cal/cm ³ ) ^1/2 .

In one embodiment, the acrylic pressure-sensitive adhesive contains a crosslinked base material made from an acrylic polymer as the base polymer.

In one embodiment, the acrylic pressure-sensitive adhesive includes an epoxy-based crosslinking agent.

In one embodiment, the epoxy-based crosslinking agent is blended in an amount of 0.6 parts by weight to 15 parts by weight based on 100 parts by weight of the acrylic polymer.

In one embodiment, the base material is a resin sheet comprising a resin having a glass transition temperature (Tg) of 25°C or more.

In one embodiment, the thickness of the base material is from 20% to 90% of the total thickness of the pressure-sensitive adhesive layer.

In one embodiment, the pressure-sensitive adhesive layer has an amount of sink of 1 µm to 35 µm as measured by the TMA in a 145°C environment.

In one embodiment, the pressure-sensitive adhesive layer generates nitrogen gas in an amount from 0.06% to 1% by weight when subjected to a heat treatment.

In one embodiment, the pressure-sensitive adhesive layer comprises: the base material; the pressure-sensitive adhesive layer disposed on one side of the base material; and a second pressure-sensitive adhesive layer disposed on a side of the base material opposite to the pressure-sensitive adhesive layer.

In one embodiment, the pressure-sensitive adhesive layer is a temporary fixing material used in a step of encapsulating a semiconductor chip in a resin.

In one embodiment, the pressure-sensitive adhesive layer is used when the encapsulating resin is cured onto the pressure-sensitive adhesive layer.

Advantageous Effects of the Invention

According to the present invention, a pressure-sensitive adhesive sheet can be provided which has moderate pressure-sensitive adhesive properties to an encapsulation resin for encapsulating a semiconductor chip therein and the semiconductor chip, can be easily separated from the encapsulation resin, hardly causes an adhesive residue when it is separated, and hardly causes a step between the semiconductor chip and the encapsulation resin caused after their detachment.

character list

• 1 Figure 12 is a schematic sectional view of a pressure-sensitive adhesive sheet according to an embodiment of the present invention.
• 2(a) 12 are a view showing an example of a case where a known pressure-sensitive adhesive sheet is used in a step of encapsulating semiconductor chips in a resin, and FIG 2 B) 12 are each a view showing an example of a case where the pressure-sensitive adhesive sheet of the present invention is used in the step of encapsulating the semiconductor chips in the resin.
• 3 Fig. 12 is a schematic sectional view of a pressure-sensitive adhesive sheet according to another embodiment of the present invention.

Description of Embodiments

A. Pressure-Sensitive Adhesive Layer Concept

The 1 Figure 12 is a schematic sectional view of a pressure-sensitive adhesive sheet according to an embodiment of the present invention. A pressure-sensitive adhesive sheet 100 comprises a base material 10 and a pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) 20 disposed on at least one side of the base material 10 . The pressure-sensitive adhesive layer contains an acrylic pressure-sensitive adhesive.

The pressure-sensitive adhesive sheet of the present invention can be suitably used as a temporary fixing material in encapsulating a semiconductor chip in a resin. In particular, the pressure-sensitive adhesive sheet of the present invention can be used as a temporary fixing material for semiconductor chips when the semiconductor chips are grouped on the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the semiconductor chips are covered with a resin (typically an epoxy-based resin) and the encapsulating resin for encapsulating the semiconductor chips in the resin is cured. After encapsulating the semiconductor chips in the resin, the pressure-sensitive adhesive layer may be separated from a structural body comprising the encapsulating resin and the semiconductor chips at a predetermined subsequent step (e.g., grinding the back surface of the encapsulating resin, pattern formation, pad formation, or chip formation (cutting)). be replaced. The epoxy equivalent of the encapsulating resin is, for example, 50 g/eq. up to 500 g/eq.

The amount of sinking of the pressure-sensitive adhesive layer measured with a TMA in a 23°C environment is 5 µm or less. In addition, the T ₂ relaxation time (T _2s ) of an S component obtained by the pulse NMR of the pressure-sensitive adhesive layer is 45 µs or less. According to the pressure-sensitive adhesive sheet having such features, when the pressure-sensitive adhesive sheet is peeled off after encapsulating a semiconductor chip in a resin, a step is prevented from occurring on the pressure-sensitive adhesive sheet between the semiconductor chip and the encapsulating resin.

Possible causes for the occurrence of the step between the semiconductor chip and the encapsulating resin described above include: migration of a pressure-sensitive adhesive layer component to the encapsulating resin; and embedding the semiconductor chip in the pressure-sensitive adhesive layer by a force applied to the semiconductor chip when it is encapsulated in the resin. The causes are with reference to the 2(a) described in more detail. The 2(a) 12 are each an illustration of an example of a case where a known pressure-sensitive adhesive sheet 100' is used in encapsulating semiconductor chips in a resin. The pressure-sensitive adhesive sheet 100' includes a pressure-sensitive adhesive layer, and the outer surface of the pressure-sensitive adhesive layer is used as a bonding surface. A conventional method for encapsulating the semiconductor chips in the resin is as described below. First, semiconductor chips 1 are glued onto the pressure-sensitive adhesive layer 100' (ai). Thereafter, a composition 2' containing a monomer serving as a precursor of an encapsulating resin 2 is applied so that the semiconductor chips 1 are encapsulated therein (a-ii), and then the composition 2' is cured (a-iii). For example, a composition containing a naphthalene-type bifunctional epoxy resin (epoxy equivalent: 144) is used as the composition. Next, the pressure-sensitive adhesive sheet 100' is peeled off from a structural body A comprising the semiconductor chips 1 and the encapsulating resin 2 at a predetermined subsequent step (a-iv). In such operations, in a step in the 2 (a-ii) and a step shown in FIG 2 (a-iii) are performed, component migration occurs between the pressure-sensitive adhesive layer and the encapsulating resin, so that a mixed phase of a pressure-sensitive adhesive component and an encapsulating resin component is formed in the encapsulating resin. When the mixed phase is formed, the mixed phase is destroyed upon peeling off of the pressure-sensitive adhesive sheet, and thus part of the encapsulating resin is peeled off together with the pressure-sensitive adhesive sheet. As a result, a step occurs between each of the semiconductor chips and the encapsulation resin. In addition, in the step that is in the 2 (a-ii) and the step shown in FIG 2 (a-iii), a part of the semiconductor chips is embedded in the pressure-sensitive adhesive layer by a force applied to the semiconductor chips. The embedding of the semiconductor chips in the pressure-sensitive adhesive layer is also responsible for the step between each of the semiconductor chips and the encapsulation resin.

In the present invention, when the sinking amount of the pressure-sensitive adhesive layer measured with a TMA in an environment at 23°C is adjusted to 5 µm or less, the migration of a pressure-sensitive adhesive layer component to the encapsulating resin and the embedding of the semiconductor chips in the pressure-sensitive adhesive layer ( in particular the embedding of the semiconductor chips in the pressure-sensitive adhesive layer) can be prevented ( 2 B) ). In addition, if the T ₂ relaxation time (T _2s ) of the S component, the obtained by the pulse NMR of the pressure-sensitive adhesive layer is set to 45 µs or less, the migration of the pressure-sensitive adhesive layer component to the encapsulating resin and the embedding of the semiconductor chips in the pressure-sensitive adhesive layer (particularly, the migration of the pressure-sensitive adhesive layer component to the encapsulating resin) can be prevented ( 2 B) ).

The amount of sinking of the pressure-sensitive adhesive layer measured with a TMA in an environment at 23°C is preferably 4 μm or less, more preferably 3.5 μm or less, still more preferably 3 μm or less. When the sinking amount is within such ranges, the effect of the present invention becomes significant. Although the amount of sinking of the pressure-sensitive adhesive layer measured with the TMA in the environment at 23°C is preferably as small as possible, its lower limit is preferably 0.1 µm (more preferably 0.01 µm). A sinking amount within these ranges can be obtained, for example, by appropriately adjusting the composition of the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer and the structure (particularly, crosslinking density) of a base polymer in the pressure-sensitive adhesive.

The expression "sinking degree of the pressure-sensitive adhesive layer measured with a TMA in an environment at 23 °C" means a sinking degree 60 minutes from the time at which a sample with the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) was brought into contact with a thermomechanical analyzer is. The conditions for the measurement are set as follows: the sample is caused to permeate the layer; the nitrogen gas flow rate is 50.0 ml/min; and the indentation load is 0.01 N. In addition, when the pressure-sensitive adhesive sheet includes the pressure-sensitive adhesive layer only on one side of the base material (i.e., when the sheet is free of a second pressure-sensitive adhesive layer, which will be described later), the measurement is performed after a standard pressure-sensitive adhesive layer has been formed on the surface of the base material opposite to the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer). The standard pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer having a thickness of 45 µm formed by applying a composition for forming a pressure-sensitive adhesive layer prepared by mixing 100 parts by weight of an acrylic copolymer (a copolymer of 2-ethylhexyl acrylate (2EHA), ethyl acrylate (EA ), methyl methacrylate (MMA) and 2-hydroxyethyl acrylate (HEA), 2EHA constituent unit:EA constituent unit:MMA constituent unit:HEA constituent unit = 30:70:5:5 (weight ratio) (molecular weight (Mw = 450000)), 10 parts by weight of a tackifier (manufactured by Yasuhara Chemical Co., Ltd., product name: "MIGHTY ACE G125"), 2 parts by weight of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name: "CORONATE L"), 30 parts by weight of thermally expandable microspheres ( manufactured by Matsumoto Yushi-Seiyaku Co., Ltd., product name: “MATSUMOTO MICROSPHERE F-190D”) and toluene.

The amount of sinking of the pressure-sensitive adhesive layer, measured with a TMA in an environment at 145°C, is preferably from 1 µm to 35 µm, more preferably from 1 µm to 34 µm, even more preferably from 2 µm to 34 µm. When the sinking amount is within such ranges, the effect of the present invention becomes significant. Furthermore, even when the sheet is placed in a high-temperature environment (e.g., a heat treatment environment when encapsulating a semiconductor chip in a resin), embedding of the semiconductor chip in the pressure-sensitive adhesive layer is prevented.

The 3 Fig. 12 is a schematic sectional view of a pressure-sensitive adhesive sheet according to another embodiment of the present invention. A pressure-sensitive adhesive layer 200 further includes a second pressure-sensitive adhesive layer 30 on the side of the base material 10 opposite the pressure-sensitive adhesive layer 20. That is, the pressure-sensitive adhesive layer 200 includes the pressure-sensitive adhesive layer 20, the base material 10, and the second pressure-sensitive adhesive layer 30 in the order named. When the pressure-sensitive adhesive sheet 200 comprises the second pressure-sensitive adhesive layer 30, when encapsulated in a resin on a base, the sheet can be arranged with excellent fixability by sticking the second pressure-sensitive adhesive layer 30 side to the base.

In one embodiment, the second pressure-sensitive adhesive layer contains thermally expandable microspheres. The thermally expandable microspheres can expand at a given temperature. When the pressure-sensitive adhesive layer containing such thermally expandable microspheres is heated to a predetermined temperature or more, the thermally expandable microspheres expand to cause unevenness on their pressure-sensitive adhesive surface (ie, the surface of the second pressure-sensitive adhesive layer). Consequently, the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer decreases or disappears. When the second pressure-sensitive adhesive layer containing the thermally expandable microspheres is formed when the pressure-sensitive adhesive sheet is fixed (when it is fixed to a base), a required adhesive property is obtained and when the pressure-sensitive adhesive sheet is peeled off (eg, when it is peeled off from the base). their pressure-sensitive adhesive strength is reduced or disappearance is caused by heating them, and thus satisfactory releasability is obtained.

The pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer of the present invention at 23°C when the pressure-sensitive adhesive layer is adhered to polyethylene terephthalate is preferably from 0.05 N/20 mm to 10 N/20 mm, more preferably from 0.1 N/20 mm to 10 N /20 mm, even more preferably from 0.1 N/20 mm to 5 N/20 mm, particularly preferably from 0.2 N/20 mm to 2 N/20 mm, in particular from 0.2 N/20 mm to 1 N/20mm. When the pressure-sensitive adhesive strength is within such ranges, a pressure-sensitive adhesive sheet which can preferably fix an adherend (e.g., a semiconductor chip) and is prevented from causing adhesive residue upon peeling thereof can be obtained. As used herein, "pressure-sensitive adhesive strength at 23°C when the pressure-sensitive adhesive layer is adhered to polyethylene terephthalate" refers to the pressure-sensitive adhesive strength measured by: adhering the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (measuring 20 mm wide by 140 mm long) to a Polyethylene terephthalate film (thickness: 25 µm) (adhesion conditions: one pass back and forth with a 2 kg roller); allowing the resulting sample to stand at an ambient temperature of 23°C for 30 minutes; and then subjecting the sample to a tensile test (peeling rate: 300 mm/min, peeling angle: 180°).

The shear bond strength B of the pressure-sensitive adhesive layer of the present invention at 150°C when a silicon chip is adhered to the pressure-sensitive adhesive layer is preferably 500 g or more, more preferably from 700 g to 1500 g, still more preferably from 800 g to 1200 g. When the shear bond strength is within such ranges, the pressure-sensitive adhesive of the pressure-sensitive adhesive layer has high cohesive strength and has preferable pressure-sensitive adhesive strength even at high temperatures (e.g., in a heating step for curing an encapsulating resin), and the positional displacement of an adherend (e.g., a semiconductor chip) that disposed on the pressure-sensitive adhesive sheet can be prevented. The shear bond strength can be measured by: vertically sticking the mirror finish surface of the silicon chip (size: 5 mm by 5 mm) to the pressure-sensitive adhesive layer so that no chip corner can be brought into contact with the layer; then heating the resultant assembly at 130°C for 30 minutes so that the silicon chip is brought into close contact with the surface of the pressure-sensitive adhesive layer; then applying an external force in a horizontal direction to the chip at a measurement temperature (150°C in the case of measuring shear bond strength B) at a shear rate of 500 µm/s so that a stress-displacement curve is provided; and reading the maximum breaking load from the curve. For example, Dage 4000 manufactured by Nordson Corporation is used as the measuring device. In addition, a measurement terminal can be placed at a height of 250 µm above the surface of the pressure-sensitive adhesive layer when measuring.

The shear bond strength of the pressure-sensitive adhesive layer of the present invention at 190°C when a silicon chip is adhered to the pressure-sensitive adhesive layer is preferably from 300 g to 1000 g, more preferably from 350 g to 750 g, still more preferably from 400 g to 600 g. When the shear bond strength is within such ranges, in the case where the pressure-sensitive adhesive layer comprises the second pressure-sensitive adhesive layer containing the thermally expandable microspheres, an adherend can be preferentially fixed on the pressure-sensitive adhesive layer when the layer is caused to have its releasability on the side of the second pressure-sensitive adhesive layer, i.e., when the thermally expandable microspheres are heated so that they are expanded.

The thickness of the pressure-sensitive adhesive layer of the present invention is preferably from 3 µm to 300 µm, more preferably from 5 µm to 150 µm, even more preferably from 10 µm to 100 µm.

B. Pressure sensitive adhesive layer

The pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive containing the base polymer. As described above, the T ₂ relaxation time (T _2s ) of the S component obtained by the pulse NMR of the pressure-sensitive adhesive layer is 45 µs or less. The relaxation time has the following meaning: an energy suitable for exciting an atom serving as a measurement subject gas is applied in a pulse NMR measurement, and then a period of time required for the excited atom (group ) returns to its ground state when the relaxation time is used. What kind of excited state the atom (group) is brought into can be adjusted by the amount of energy that is applied and the period of time of application. In addition, it is known that the excited atom (group) returns to its ground state via any of various energy relaxation mechanisms, and the relaxation time is determined according to the relaxation mechanism (e.g., "Modern NMR Techniques for Chemistry Research", Kagaku-Dojin Publishing Company, Inc. ( 1997)). The inventors of the present invention excited a ¹ H atom of the acrylic pressure-sensitive adhesive (essentially an acrylic polymer in the pressure-sensitive adhesive) under the following conditions, measured its relaxation behavior after the excitement, and analyzed the measured values. As a result, the inventors have found that the T ₂ relaxation time (T _2s ) of the S component from the measured values is useful as information indicating molecular motion related to the extent to which the base polymer (typically the acrylic polymer) in is crosslinked with the pressure-sensitive adhesive to form the pressure-sensitive adhesive layer. The inventors also found that the above effect is obtained by fixing the T ₂ relaxation time (T _2s ) of the S component. A shorter T _2s represents a state where molecular movement related to the extent to which the base polymer is crosslinked is restricted, i.e., represents a state where crosslinking progresses so that the degree of freedom of movement in of the whole of the polymer is reduced. In the acrylic pressure-sensitive adhesive in such a state, a gap between molecules of the base polymer is small and thus migration of the pressure-sensitive adhesive layer component to an encapsulating resin and migration of a low-molecular weight component in the encapsulating resin to the pressure-sensitive adhesive layer are prevented. As a result, when the pressure-sensitive adhesive sheet is peeled off after encapsulating a semiconductor chip in the resin, a step is prevented from occurring on the pressure-sensitive adhesive sheet between the semiconductor chip and the encapsulating resin.

The T ₂ relaxation time (T _2s ) of the S component obtained by the pulse NMR of the pressure-sensitive adhesive layer is preferably from 10 µs to 50 µs, more preferably from 10 µs to 45 µs, still more preferably from 10 µs up to 40 µs. When the relaxation time is within such ranges, the above effect becomes significant.

• M(t): Freier Induktionszerfall
• α: Protonenanteil (%) einer Komponente mit einer kurzen Relaxationszeit (S-Komponente)
• T_2s: T₂-Relaxationszeit (ms) der S-Komponente
• β: Protonenanteil (%) einer Komponente mit einer langen Relaxationszeit (L-Komponente)
• T_2L: T₂-Relaxationszeit (ms) der L-Komponente
• t: Untersuchungszeit (ms)
• Wa: Formfaktor (= 1)

The T ₂ relaxation time (T _2s ) of the S component obtained by the pulse NMR can be determined by: measuring 100 mg of the pressure-sensitive adhesive layer serving as a measurement sample by a solid-state echo method so that a T ₂ - relaxation curve is provided; and fitting the T ₂ relaxation curve to the following equation (1). $$\text{M}\left(\text{t}\right)=\mathrm{a}\cdot \text{ex}\left(-\left(1/\text{wha}\right){\left({\text{t/d}}_{2\text{s}}\right)}^{\text{wha}}\right)+\mathrm{\beta }\cdot \text{ex}\left(-\left(1/\text{wha}\right){\left({\text{t/d}}_{2\text{L}}\right)}^{\text{wha}}\right)$$

• M(t): Free induction decay
• α: Proton fraction (%) of a component with a short relaxation time (S component)
• T _2s : T ₂ relaxation time (ms) of the S component
• β: Proton fraction (%) of a component with a long relaxation time (L component)
• T _2L : T ₂ relaxation time (ms) of the L component
• t: examination time (ms)
• Wa: form factor (= 1)

The measurement conditions in the above measurement are as described below. • 90° pulse width: 2.1µs • Repeat time: 1s • Number of Samples: 32 times • Measuring temperature: 30℃

The thickness change ratio of the pressure-sensitive adhesive layer after 4-tert-butylphenyl glycidyl ether has been dropped onto the surface of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer has been allowed to stand for 1 minute is preferably 160% or less, more preferably 150% or less, even more preferably 120% or less, especially preferably 100% or less. Such a pressure-sensitive adhesive layer in which the thickness change ratio is within such ranges has a high crosslinking density, and thus component migration between the pressure-sensitive adhesive layer and an encapsulating resin is prevented. As a result, at the time of peeling off the pressure-sensitive adhesive sheet after encapsulating a semiconductor chip in the resin, a step is prevented from occurring on the pressure-sensitive adhesive sheet between the semiconductor chip and the encapsulating resin. Although the thickness change ratio is preferably as small as possible, its lower limit is, for example, 20% (preferably 10%). The Dickenn Change ratio (and a thickness change amount to be described later) can be set within the ranges, for example, preferably by selecting the base polymer (typically the acrylic polymer) in the acrylic pressure-sensitive adhesive. For example, the use of an acrylic polymer having many (eg, 4 or more, preferably 8 or more) carbon atoms enables formation of a pressure-sensitive adhesive layer whose thickness change ratio (and a thickness change amount to be described later) are small. The thickness change ratio is determined in the following manner: A predetermined amount (0.02 g when a syringe with a diameter of 22 mm is used) of 4-tert-butylphenyl glycidyl ether is dropped onto the surface of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is exposed to an atmosphere left to stand at 23°C and 50% relative humidity (RH) for 1 minute, after which the 4-tert-butylphenyl glycidyl ether is wiped off; and the ratio is determined from the expression "(Dt - It)/It" by using the thickness (Dt) of the spot after wiping and the thickness (It) of the spot before dripping.

The amount of change in thickness of the pressure-sensitive adhesive layer after the 4-tert-butylphenylglycidyl ether has been dropped onto the surface of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer has been allowed to stand for 1 minute is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, more preferably 6 µm or less. Such a pressure-sensitive adhesive layer in which the amount of change in thickness is within such ranges has a high crosslinking density, and thus component migration between the pressure-sensitive adhesive layer and an encapsulating resin is prevented. As a result, when the pressure-sensitive adhesive sheet is peeled off after encapsulating a semiconductor chip in the resin, a step is prevented from occurring on the pressure-sensitive adhesive sheet between the semiconductor chip and the encapsulating resin. Although the amount of change in thickness is preferably as small as possible, its lower limit is, for example, 3 µm (preferably 1 µm). The thickness change amount is defined by the expression "Dt - It" using Dt and It described above.

The gel fraction of the pressure-sensitive adhesive layer is preferably 75% or more, more preferably 85% or more, even more preferably 90% or more. When the gel content is within such ranges, a pressure-sensitive adhesive layer can be obtained in which the molecular movement of its base polymer is preferably restricted by its crosslinking, and thus component migration between the pressure-sensitive adhesive layer and an encapsulating resin is prevented. Although the gel fraction of the pressure-sensitive adhesive layer is preferably as high as possible, its upper limit is 99.5%, for example. The gel content of the layer is determined as follows: Its crosslinked pressure-sensitive adhesive is immersed in ethyl acetate for 7 days and is then dried, after which the gel content is determined from the expression "(dry weight after immersion)/(dry weight before immersion) × 100".

• • Trägergase: O₂ (300 mL/min) und Ar (300 mL/min)
• • Standardprobe: Pyridin/Toluol-Lösung
• • Detektor: Chemilumineszenzdetektor für verminderten Druck
• • Bereich: Hohe Konzentration

The generation amount of nitrogen gas when the pressure-sensitive adhesive layer is subjected to heat treatment is preferably from 0.06% to 1.0% by weight, more preferably from 0.06% to 0.9% by weight. . If the generation amount of nitrogen gas when the pressure-sensitive adhesive layer is subjected to the heat treatment is within such ranges, the acrylic pressure-sensitive adhesive has sufficient cohesive strength so that the migration of a component of an encapsulating resin with a low molecular weight to the pressure-sensitive adhesive layer is prevented. Consequently, a mixed phase of the pressure-sensitive adhesive layer component and the encapsulating resin component is not formed, and thus a step hardly occurs at an interface between a semiconductor chip and the encapsulating resin. The amount of nitrogen gas when the pressure-sensitive adhesive layer is subjected to the heat treatment is determined as follows: 2 mg of the pressure-sensitive adhesive layer is collected and placed on a ceramic plate, followed by weighing with a microbalance; and the resultant sample is heated under the conditions of a thermal decomposition furnace temperature of 800°C and an oxidation furnace temperature of 900°C, and the amount of generated nitrogen gas is measured with a total nitrogen (TN) trace analyzer. The various conditions in the measurement can be set in the manner described below.

• • Carrier gases: O ₂ (300 mL/min) and Ar (300 mL/min)
• • Standard sample: pyridine/toluene solution
• • Detector: Reduced pressure chemiluminescence detector
• • Area: High concentration

The thickness of the pressure-sensitive adhesive layer is preferably from 1 μm to 50 μm, more preferably from 3 μm to 30 μm, even more preferably from 5 μm to 20 μm. If the thickness is within such ranges, a pressure-sensitive adhesive sheet can be obtained in which a semiconductor chip is hardly embedded in a resin even when pressurized in a packaging step.

The elastic modulus of the pressure-sensitive adhesive layer, measured at 25°C by a nanoindentation method, is preferably less than 100 MPa, more preferably from 0.1 MPa to 50 MPa, even more preferably from 0.1 MPa to 10 MPa. If the elastic modulus is within such ranges, a pressure-sensitive adhesive sheet having an appropriate pressure-sensitive adhesive strength can be obtained. The Young's modulus measured by the nano-indentation method refers to a Young's modulus determined by an applied stress-indentation depth curve obtained by continuously measuring a stress applied to an indentation member and the indentation depth thereof when the indentation member is pressed into the sample during a period from the start of loading to the end of unloading is obtained. Here, the Young's modulus measured by the nanoindentation method refers to a Young's modulus measured in the manner described above under the measurement conditions of a load of 1 mN, a loading and unloading rate of 0.1 mN/s, and a holding time of 1 s is measured.

The tensile modulus of the pressure-sensitive adhesive layer at 25°C is preferably less than 100 MPa, more preferably from 0.1 MPa to 50 MPa, even more preferably from 0.1 MPa to 10 MPa. When the tensile modulus of elasticity is within such ranges, a pressure-sensitive adhesive sheet having an appropriate pressure-sensitive adhesive strength can be obtained. Tensile elastic modulus can be measured according to JIS K 7161:2008.

The probe toughness value of the pressure-sensitive adhesive layer is preferably 50 N/5 mmφ or more, more preferably 75 N/5 mmφ or more, still more preferably 100 N/5 mmφ or more. When the probe toughness value is within such ranges, positional displacement of an adherend (e.g., a semiconductor chip) placed on the pressure-sensitive adhesive sheet can be prevented. The probe toughness value is measured under the conditions of a probe working speed of 30 mm/min, a probe speed of 30 mm/min, a contact load of 100 gf, a contact holding time of 1 second, and a sample area of 5 mmφ SUS.

The sp value of the base polymer is preferably from 10 (cal/cm ³ ) ^1/2 to 30 (cal/cm ³ ) ^1/2 , more preferably from 15 (cal/cm ³ ) ^1/2 to 25 (cal/cm ³ ) ^1/2 , more preferably from 18 (cal/cm ³ ) ^1/2 to 20 (cal/cm ³ ) ^1/2 . When the sp value is within such ranges, component migration between the pressure-sensitive adhesive layer and an encapsulating resin is preferably prevented.

(acrylic pressure sensitive adhesive)

The acrylic pressure-sensitive adhesive is, for example, an acrylic pressure-sensitive adhesive obtained by using an acrylic polymer (homopolymer or copolymer) using one kind or two or more kinds of (meth)acrylic acid alkyl esters as monomer components as a prepolymer and a crosslinked base material of the prepolymer as a base polymer becomes. Here, the "base polymer" in the acrylic pressure-sensitive adhesive in the pressure-sensitive adhesive layer means a polymer formed by crosslinking the pre-polymer (uncrosslinked polymer). In one embodiment, the base polymer comprises a crosslinked base material structure formed from the acrylic polymer and an epoxy-based crosslinking agent.

Specific examples of the (meth)acrylic acid alkyl ester include (meth)acrylic acid C1-20 alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth) acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2- Ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl( meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate and eicosyl (meth)acrylate. Of these, a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 4 to 20 (more preferably 6 to 20, particularly preferably 8 to 18) carbon atoms is preferred, and 2-ethylhexyl (meth)acrylate is more preferred.

In one embodiment, a (meth)acrylic acid alkyl ester having a linear or branched alkyl group with 4 or more (preferably 8 or more) carbon atoms is used. The use of the (meth)acrylic acid alkyl ester preferably prevents component migration between the pressure-sensitive adhesive layer and an encapsulating resin.

The acrylic polymer (prepolymer) may optionally contain a unit corresponding to any other monomer component copolymerizable with the (meth)acrylic acid alkyl ester for modifying cohesive strength, heat resistance, crosslinkability or the like. Examples of such a monomer component include: carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; Hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate and ( 4-hydroxymethylcyclohexyl)methyl methacrylate; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate and (meth)acryloyloxynaphthalenesulfonic acid; (N-substituted) amide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide and N-methylolpropane(meth) acrylamide; aminoalkyl (meth)acrylate-based monomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylate-based monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide and N-laurylitaconimide; succinimide-based monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide and N-(meth)acryloyl-8-oxyoctamethylene succinimide; vinyl-based monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxamides, styrene, α-methylstyrene and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic acid ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate and methoxypolypropylene glycol (meth)acrylate; acrylic acid ester-based monomers each having, for example, a heterocycle, a halogen atom or a silicon atom, such as tetrahydrofurfuryl (meth)acrylate, fluoro(meth)acrylate and silicone (meth)acrylate; polyfunctional monomers such as hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth )acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, polyester acrylate and urethane acrylate; olefin-based monomers such as isoprene, butadiene and isobutylene; and vinyl ether-based monomers such as vinyl ether. These monomer components can be used alone or in a combination thereof.

In one embodiment, the acrylic polymer (prepolymer) further contains a constituent unit "a" derived from a monomer having a glass transition temperature (Tg) from -5 °C to 150 °C (preferably from 50 °C to 150 °C, more preferably from 80°C to 120°C) when converted to a homopolymer. The inclusion of such a constituent unit "a" can provide an acrylic polymer in which the molecular movement of the acrylic polymer is restricted and thus the T ₂ relaxation time (T _2s ) of an S component obtained by the pulse NMR thereof is preferably adjusted . In addition, a pressure-sensitive adhesive sheet excellent in low-temperature pressure-sensitive adhesive properties can be obtained. The content of the constituent unit "a" is preferably from 0.1% to 20% by weight, more preferably from 1% to 10% by weight, particularly preferably from 1.5% to 1.5% by weight 8% by weight, especially from 3% to 6% by weight, based on all the constituent units to form the acrylic polymer.

Examples of the monomer having a glass transition temperature (Tg) of -5°C to 150°C include 2-hydroxyethyl acrylate (Tg: -3°C), 2-hydroxyethyl methacrylate (Tg: 77°C), acrylic acid (Tg: 102 °C), cyclohexyl methacrylate (Tg: 83 °C), dicyclopentanyl acrylate (Tg: 120 °C), dicyclopentanyl methacrylate (Tg: 175 °C), isobornyl acrylate (Tg: 94 °C), isobornyl methacrylate (Tg: 150 °C), t-butyl methacrylate (Tg: 118 °C), methyl methacrylate (Tg: 105 °C), styrene (Tg: 80 °C), acrylonitrile (Tg: 97 °C) and N-acryloylmorpholine (Tg: 145 °C). Of these, methyl methacrylate is preferred when the visibility of an adherend is to be improved when it is processed, since methyl methacrylate improves the transparency of the pressure-sensitive adhesive layer. In addition, acrylic acid is preferable when strong pressure-sensitive adhesion is required, since acrylic acid strongly adheres to the adherend due to an intermolecular interaction between itself and the adherend. Further, hydroxyethyl acrylate is preferred for relaxation time adjustment because hydroxyethyl acrylate has high reactivity with various crosslinking agents.

In one embodiment, the acrylic polymer (prepolymer) further contains a constituent unit derived from a hydroxyl group-containing monomer. The content of the constituent unit used by a hydroxyl group-containing monomer is preferably from 0.1% to 20% by weight, more preferably from 0.5% to 10% by weight, particularly preferably from 1% by weight to 7% by weight based on all constituent units to form the acrylic polymer.

The acrylic pressure-sensitive adhesive can contain any suitable additive, if desired. Examples of the additive include a crosslinking agent, a tackifier, a plasticizer (e.g., a trimellitic acid ester-based plasticizer or a pyromellitic acid ester-based plasticizer), a pigment, a dye, a filler, an antiaging agent, a conductive material, an antistatic agent, a UV absorber, a light stabilizer, a release modifier, a softening agent, a surfactant, a flame retardant and an antioxidant.

Examples of the crosslinking agent in the acrylic pressure-sensitive adhesive include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a melamine-based crosslinking agent, a peroxide-based crosslinking agent, a urea-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, a carbodiimide-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, and an amine-based crosslinking agent.

In one embodiment, the blending amount of the crosslinking agent is preferably from 0.08 molar equivalent to 2 molar equivalent, more preferably from 0.1 molar equivalent to 1 molar equivalent, based on the carboxyl groups of the acrylic polymer (prepolymer). When the amount is within such ranges, an acrylic pressure-sensitive adhesive having a high crosslink density can be formed, and thus component migration between the pressure-sensitive adhesive layer and an encapsulating resin is preferably prevented. Here, the blending amount of the crosslinking agent means the content of the crosslinking agent before crosslinking of the acrylic polymer.

Specific examples of the isocyanate-based crosslinking agent in the acrylic pressure-sensitive adhesive include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and xylylene diisocyanate; and isocyanate adducts such as a trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "CORONATE L"), a trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., product name " CORONATE HL”) and an isocyanurate form of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., product name “CORONATE HX”). The blending amount of the isocyanate-based crosslinking agent can be adjusted to any suitable amount according to a desired pressure-sensitive adhesive strength, and the amount is typically from 0.1 part to 20 parts by weight, more preferably from 1 part to 10 parts by weight, based on 100 parts by weight of the acrylic polymer. When the amount is within such ranges, a pressure-sensitive adhesive sheet in which the amount of the residual carboxyl group of a component in its pressure-sensitive adhesive layer is small can be obtained. Here, the blending amount of the crosslinking agent means the content of the crosslinking agent before the acrylic polymer is crosslinked.

In one embodiment, an epoxy-based crosslinking agent is preferably used as the crosslinking agent. The use of the epoxy-based crosslinking agent can provide a pressure-sensitive adhesive layer which can preferably reduce a step between a semiconductor chip and an encapsulating resin. In addition, a pressure-sensitive adhesive layer having a high cohesive strength can be formed, and thus a positional shift of an adherend can be prevented more effectively.

Examples of the epoxy-based crosslinking agent in the acrylic pressure-sensitive adhesive include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company , Inc., product name: "TETRAD-C"), 1,6-hexanediol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., product name: "Epolite 1600"), neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., product name : "Epolite 1500NP"), ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., product name: "Epolite 40E"), propylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., product name: "Epolite 70P"), polyethylene glycol diglycidyl ether (manufactured by NOF Corporation, product name: "EPIOL E-400"), polypropylene glycol diglycidyl ether (manufactured by NOF Corporation, product name: "EPIOL P-200"), sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, product name: "Denacol EX-61 1"), Glycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, product name: “Denacol EX-314"), pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, product name: "Denacol EX-512"), sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bis phenol S-diglycidyl ether and an epoxy-based resin having two or more epoxy groups in a molecule thereof. The blending amount of the epoxy-based crosslinking agent can be adjusted to any suitable amount according to a desired pressure-sensitive adhesive strength, and the amount is typically from 0.01 part by weight to 50 parts by weight, more preferably from 0.6 part by weight to 15 parts by weight, even more preferably from 2 parts by weight to 13 parts by weight, more preferably from 3 parts by weight to 10 parts by weight based on 100 parts by weight of the acrylic polymer. When the amount is within such ranges, a pressure-sensitive adhesive sheet in which the amount of the residual carboxyl group of a component in its pressure-sensitive adhesive layer is small can be obtained. Here, the blending amount of the crosslinking agent means the content of the crosslinking agent before the acrylic polymer is crosslinked.

In one embodiment, a crosslinking agent containing an N atom is used as the epoxy-based crosslinking agent. The use of the crosslinking agent containing an N atom is advantageous in that the crosslinking reaction of the acrylic polymer is easily accelerated by its catalytic action, so that the pressure-sensitive adhesive is strongly gelled.

Any suitable tackifier is used as the tackifier in the acrylic pressure sensitive adhesive. For example, a tackifying resin is used as the tackifier. Specific examples of the tackifying resin include a rosin-based tackifying resin (such as an unmodified rosin, a modified rosin, a rosin-phenol-based resin or a rosin ester-based resin), a terpene-based tackifying resin (such as e.g., a terpene-based resin, a terpene-phenol-based resin, a styrene-modified terpene-based resin, an aromatic-modified terpene-based resin, or a hydrogenated terpene-based resin), a hydrocarbon tackifying resin -Base (such as an aliphatic hydrocarbon resin, an aliphatic cyclic hydrocarbon resin, an aromatic hydrocarbon resin (e.g. a styrene-based resin or a xylene-based resin), an aliphatic/aromatic petroleum resin, an aliphatic/alicyclic petroleum resin, a hydrogenated hydrocarbon resin, a coumarone-based resin or a coumarone-indene-based resin), a phenol-based tackifying resin (such as an alkylphenol-based resin, a xylene-formaldehyde-based resin, a resol or a novolak), a ketone-based tackifying resin, a polyamide-based tackifying resin, an epoxy-based tackifying resin, and an elastomer-based tackifying resin. Of these, a rosin-based tackifying resin, a terpene-based tackifying resin, or a hydrocarbon-based tackifying resin (e.g., a styrene-based resin) is preferred. The tackifiers can be used alone or in combination. The addition amount of the tackifier is preferably 5 parts by weight to 100 parts by weight, more preferably 8 parts by weight to 50 parts by weight based on 100 parts by weight of the base polymer.

Preferably, a resin having a high softening point or a high glass transition temperature (Tg) is used as the tackifying resin. The use of a resin having a high softening point or a high glass transition temperature (Tg) makes it possible to form a pressure-sensitive adhesive layer which can have very good adhesive properties even in a high-temperature environment (e.g. in a high-temperature environment, for example, in processing when encapsulating a semiconductor chip). The softening point of the tackifier is preferably from 100°C to 180°C, more preferably from 110°C to 180°C, even more preferably from 120°C to 180°C. The glass transition temperature (Tg) of the tackifier is preferably from 100°C to 180°C, more preferably from 110°C to 180°C, even more preferably from 120°C to 180°C.

As the tackifying resin, a low polarity tackifying resin is preferably used. The use of the low polarity tackifying resin enables the formation of a pressure-sensitive adhesive layer having a low affinity for an encapsulating material. Examples of the low polarity tackifying resin include hydrocarbon-based tackifying resins such as an aliphatic hydrocarbon resin, an aliphatic cyclic hydrocarbon resin, an aromatic hydrocarbon resin (eg, a styrene-based resin or a xylene-based resin), an aliphatic/ aromatic petroleum resin, an aliphatic/alicyclic petroleum resin and a hydrogenated hydrocarbon resin. Of these, a tackifier having 5 to 9 carbon atoms is preferred. This is because such a tackifier has low polarity and is excellent in compatibility with the acrylic polymer, thus enabling formation of a pressure-sensitive adhesive layer which is not subject to any phase transition in a wide temperature range and thus has excellent stability.

The acid number of the tackifying resin is preferably 40 or less, more preferably 20 or less, even more preferably 10 or less. When the acid value is within such ranges, a pressure-sensitive adhesive layer having a low affinity for an encapsulant can be formed. The hydroxyl number of the tackifying resin is preferably 60 or less, more preferably 40 or less, even more preferably 20 or less. When the hydroxyl value is within such ranges, a pressure-sensitive adhesive layer having a low affinity for an encapsulating material can be formed.

C. Base Material

Examples of the base material include a resin sheet, a non-woven fabric, a paper, a metal foil, a woven fabric, a rubber sheet, a foam sheet, and laminates thereof (particularly, a laminate containing a resin sheet). As the resin for forming the resin layer, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polyethylene (PE), polypropylene (PP), an ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), wholly aromatic polyamide (aramid), polyimide (PI), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), a fluorine-based resin and polyetheretherketone (PEEK). Examples of the nonwoven fabric include: nonwoven fabrics made of natural fibers each having heat resistance, such as a nonwoven fabric containing Manila hemp; and synthetic resin non-woven fabrics such as a polypropylene resin non-woven fabric, a polyethylene resin non-woven fabric and an ester-based resin non-woven fabric. Examples of the metal foil include a copper foil, a stainless steel foil, and an aluminum foil. Examples of the paper include Japanese paper and kraft paper.

In one embodiment, a resin sheet comprising a resin having a glass transition temperature (Tg) of 25°C or more (more preferably 40°C or more, still more preferably 50°C or more) is preferably used as the base material. When such a resin sheet is used, the shape of the base material is maintained even after it is heated in an encapsulating step, and thus a semiconductor chip is prevented from being embedded in the resin. Examples of the resin constituting such a resin sheet include polyethylene terephthalate, polyimide and polyethylene naphthalate.

The thickness of the base material can be adjusted to any suitable thickness according to desired strength or flexibility and desired applications, for example. The thickness of the base material is preferably 1000 μm or less, more preferably from 25 μm to 1000 μm, even more preferably from 40 μm to 500 μm, particularly preferably from 60 μm to 300 μm, particularly from 80 μm to 250 μm. In one embodiment, a base material with a thickness of 25 μm or more is used. When such a base material is used, the shape of the base material is maintained even after it is pressurized in the encapsulating step, and thus embedding of a semiconductor chip in the pressure-sensitive adhesive layer is prevented.

In one embodiment, the thickness of the base material is from 20% to 90% (preferably from 20% to 89%, more preferably from 20% to 88%) of the total thickness of the pressure-sensitive adhesive layer. If the thickness is within such ranges, embedding of the semiconductor chip in the pressure-sensitive adhesive layer is prevented.

The base material can be subjected to surface treatment. Examples of the surface treatment include corona treatment, chromic acid treatment, ozone exposure, flame exposure, exposure to high voltage electric shock, ionizing radiation treatment, and coating treatment with a primer coating agent.

As the organic coating material, materials mentioned in “Plastic Hard Coat Material II” (CMC Publishing Co., Ltd., (2004)) can be exemplified. A urethane-based polymer is preferably used, and a polyurethane acrylate, polyester polyurethane or a precursor thereof is more preferably used. This is due to the following reasons: any such material can be simply coated and applied to the base material; and many kinds of the material can be selected industrially and are available inexpensively. The urethane-based polymer is, for example, a polymer made from a reacted mixture of a isocyanate monomer and an alcoholic hydroxyl group-containing monomer (eg, a hydroxyl group-containing acrylic compound or a hydroxyl group-containing ester compound). The organic coating material may contain, as an optional additive, a chain extender such as a polyamine, an anti-aging agent, an oxidation stabilizer or the like. The thickness of an organic coating layer is not particularly limited, but is, for example, suitably from about 0.1 µm to about 10 µm, preferably from about 0.1 µm to about 5 µm, more preferably from about 0.5 µm to about 5 µm.

D. Second pressure-sensitive adhesive layer

The second pressure-sensitive adhesive layer can be a pressure-sensitive adhesive layer comprising a suitable pressure-sensitive adhesive. In one embodiment, as described above, the second pressure-sensitive adhesive layer further includes the thermally expandable microspheres.

The pressure-sensitive adhesive in the second pressure-sensitive adhesive layer may be a curable pressure-sensitive adhesive (eg, an active energy ray-curable pressure-sensitive adhesive) or may be a pressure-sensitive pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive and a rubber-based pressure-sensitive adhesive. For details of the pressure-sensitive adhesive in the second pressure-sensitive adhesive layer, reference can be made to the description of, for example JP 2018-009050 A , the entire description of which is incorporated herein by reference.

As the thermally expandable microspheres, any suitable thermally expandable microspheres can be used as long as the microspheres can be expanded or expanded by heating. For example, microspheres each obtained by encapsulating a substance which easily undergoes volume increase by heating in an elastic shell can be used as the thermally expandable microspheres. Such thermally expandable microspheres can be made by any suitable method, such as a coacervation process or an interfacial polymerization process.

Examples of the substance which is liable to undergo volume increase by heating include: A low boiling point liquid such as propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, heptane , octane, petroleum ether, a halomethane or a tetraalkylsilane; and azodicarbonamide gasified by thermal decomposition.

A substance for forming the shell is, for example, a polymer formed from: a nitrile monomer such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile or fumaronitrile; a carboxylic acid monomer such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid or citraconic acid; vinylidene chloride; vinyl acetate; a (meth)acrylic ester such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl( meth)acrylate, benzyl (meth)acrylate or β-carboxyethyl acrylate; a styrenic monomer such as styrene, α-methylstyrene or chlorostyrene; or an amide monomer such as acrylamide, a substituted acrylamide, methacrylamide or a substituted methacrylamide. The polymer formed from such a monomer may be a homopolymer or may be a copolymer. Examples of the copolymer include a vinylidene chloride-methyl methacrylate-acrylonitrile copolymer, a methyl methacrylate-acrylonitrile-methacrylonitrile copolymer, a methyl methacrylate-acrylonitrile copolymer and an acrylonitrile-methacrylonitrile-itaconic acid copolymer.

As the thermally expandable microbeads, an inorganic foaming agent or an organic foaming agent can be used. Examples of the inorganic foaming agent include ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium boron hydroxide and various azides. Furthermore, examples of the organic foaming agent include: a chlorofluoroalkane-based compound such as trichloromonofluoromethane or dichloromonofluoromethane; an azo-based compound such as azobisisobutyronitrile, azodicarbonamide or barium azodicarboxylate; a hydrazine-based compound such as p-toluenesulfonyl hydrazide, diphenylsulfone-3,3'-disulfonyl hydrazide, 4,4'-oxybis(benzenesulfonyl hydrazide) or allylbis(sulfonyl hydrazide); a semicarbazide-based compound such as p-tolylenesulfonylsemicarbazide or 4,4'-oxybis(benzenesulfonylsemicarbazide); a triazole-based compound such as 5-morpholyl-1,2,3,4-thiatriazole; and an N-nitroso-based compound such as N,N'-dinitrosopentamethylenetetramine or N,N'-dimethyl-N,N'-dinitrosoterephthalamide.

Commercially available thermally expandable microspheres can be used as the thermally expandable microspheres. Specific examples of the commercially available thermally expandable microspheres include: Products sold under the product name "Matsumoto Microsphere" (Grade: F-30, F-30D, F-36D, F-36LV, F-50, F-50D, F-65 , F-65D, FN-100SS, FN-100SSD, FN-180SS, FN-180SSD, F-190D, F-260D and F-2800D) by Matsumoto Yushi-Seiyaku Co., Ltd. are available; Products sold under the product name "Expancel" (grade: 053-40, 031-40, 920-40, 909-80 and 930-120) by Japan Fillite Co., Ltd. are available; Products sold under the product name "DAIFOAM" (grade: H750, H850, H1100, S2320D, S2640D, M330, M430 and M520) by Kureha Chemical Industry Co., Ltd. are available; and products sold under the product name "ADVANCEL" (grade: EML101, EMH204, EHM301, EHM302, EHM303, EM304, EHM401, EM403 and EM501) by Sekisui Chemical Co., Ltd. are available.

The particle diameter of each of the thermally expandable microspheres before heating them is preferably from 0.5 µm to 80 µm, more preferably from 5 µm to 45 µm, still more preferably from 10 µm to 20 µm, particularly preferably from 10 µm to 15 µm. Accordingly, the particle size of the thermally expandable microspheres before heating them is preferably from 6 µm to 45 µm, more preferably from 15 µm to 35 µm in terms of average particle diameter. The particle diameter and average particle diameter described above are values determined by a particle size distribution measurement method in a laser scattering method.

It is preferable that the thermally expandable microspheres each have a moderate strength such that rupture does not occur until a volume expansion ratio is preferably 5 times or more, more preferably 7 times or more, still more preferably 10 times times or more achieved. When such thermally expandable microspheres are used, the pressure-sensitive adhesive strength can be reduced efficiently by the heat treatment.

The content of the thermally expandable microspheres in the pressure-sensitive adhesive layer can be appropriately adjusted according to, for example, a desired property which reduces the pressure-sensitive adhesive strength of the layer. The content of the thermally expandable microspheres is, for example, from 1 part by weight to 150 parts by weight, preferably from 10 parts by weight to 130 parts by weight, more preferably from 25 parts by weight to 100 parts by weight relative to 100 parts by weight of a base polymer for forming the second pressure-sensitive adhesive layer.

When the pressure-sensitive adhesive layer contains the thermally expandable microspheres, the arithmetic surface roughness Ra of the pressure-sensitive adhesive layer before expanding the thermally expandable microspheres (i.e., before heating them) is preferably 500 nm or less, more preferably 400 nm or less, even more preferably 300 nm or less . When the arithmetic surface roughness is within such ranges, a pressure-sensitive adhesive sheet excellent in adhesion to an adherend can be obtained. The pressure-sensitive adhesive layer with excellent surface smoothness as described above can be obtained, for example, by adjusting the thickness of the pressure-sensitive adhesive layer within the above ranges or, when the pressure-sensitive adhesive layer comprises another pressure-sensitive adhesive layer, by applying and transferring the pressure-sensitive adhesive layer to a release liner. As described in Section A, when the pressure-sensitive adhesive layer of the present invention further comprises a further pressure-sensitive adhesive layer, the further pressure-sensitive adhesive layer may contain thermally expandable microspheres. Further, when the pressure-sensitive adhesive layer contains the thermally expandable microspheres, the arithmetic surface roughness Ra of the pressure-sensitive adhesive layer is preferably within the ranges.

When the pressure-sensitive adhesive layer contains the thermally expandable microspheres, the pressure-sensitive adhesive layer preferably contains a pressure-sensitive adhesive comprising a base polymer whose dynamic storage modulus at 80°C is within the range of from 5 kPa to 1 MPa (more preferably from 10 kPa to 0.8 MPa). . Such a pressure-sensitive adhesive layer enables the formation of a pressure-sensitive adhesive layer which has poor pressure-sensitive adhesive properties before it is heated and whose pressure-sensitive adhesive strength is easily reduced by heating. The dynamic storage modulus of elasticity can be measured with a dynamic viscoelasticity measuring device (e.g. a product available under the product name "ARES" from Rheometric Scientific FE) under the measurement conditions of a frequency of 1 Hz and a temperature rise rate of 10 °C/min .

E. Method of Making a Pressure-Sensitive Adhesive Sheet

The pressure-sensitive adhesive sheet of the present invention can be made by any suitable method. A method of making the pressure-sensitive adhesive sheet of the present invention is exemplary a method for directly applying a composition containing the acrylic pressure-sensitive adhesive to the base material, or a method comprising applying the composition containing the acrylic pressure-sensitive adhesive to any suitable base material and transferring the applied layer thus formed includes the base material. The composition containing the acrylic pressure sensitive adhesive can contain any suitable solvent.

When forming a pressure-sensitive adhesive layer containing thermally expandable microspheres, the pressure-sensitive adhesive layer can be formed by applying to the base material a composition containing the thermally expandable microspheres, a pressure-sensitive adhesive, and any suitable solvent. Alternatively, the pressure-sensitive adhesive layer containing the thermally expandable microspheres can be formed by sprinkling the thermally expandable microspheres onto a pressure-sensitive adhesive-coated layer and then embedding the thermally expandable microspheres in the pressure-sensitive adhesive with a laminator or the like.

As the method of applying each of the pressure-sensitive adhesive and the respective compositions described above, any suitable application method can be employed. Each layer can be formed, for example, by drying the pressure-sensitive adhesive or composition after it has been applied. The application method is, for example, an application method involving the use of a manifold coater, a die coater, a gravure coater, or an applicator. A drying method is, for example, natural drying or heat drying. The heating temperature when performing heat drying can be set at any appropriate temperature according to the properties of a substance to be dried.

examples

Hereinafter, the present invention is specifically described by way of examples. However, the present invention is by no means restricted to these examples. Evaluation methods in examples are as described below. In addition, the terms "part(s)" and "%" in examples are by weight unless otherwise specified.

(1) T ₂ relaxation time (T _2s ) of S component obtained by a pulse NMR of the pressure-sensitive adhesive layer

• M(t): Freier Induktionszerfall
• α: Protonenanteil (%) einer Komponente mit einer kurzen Relaxationszeit (S-Komponente)
• T_2s: T₂-Relaxationszeit (ms) der S-Komponente
• β: Protonenanteil (%) einer Komponente mit einer langen Relaxationszeit (L-Komponente)
• T_2L: T₂-Relaxationszeit (ms) der L-Komponente
• t: Untersuchungszeit (ms)
• Wa: Formfaktor (= 1)

The T ₂ relaxation time (T _2s ) of an S component obtained by the pulse NMR of the pressure-sensitive adhesive layer was determined by: measuring 100 mg of the pressure-sensitive adhesive layer serving as a measurement sample with a product sold under the product name “ TD-NMR the minispec mq20” is available from Bruker, by a solid state echo method to provide a T ₂ relaxation curve; and fitting the T ₂ relaxation curve to the following equation (1). $$\text{M}\left(\text{t}\right)=\mathrm{a}\cdot \text{ex}\left(-\left(1/\text{wha}\right){\left({\text{t/d}}_{2\text{s}}\right)}^{\text{wha}}\right)+\mathrm{\beta }\cdot \text{ex}\left(-\left(1/\text{wha}\right){\left({\text{t/d}}_{2\text{L}}\right)}^{\text{wha}}\right)$$

• M(t): Free induction decay
• α: Proton fraction (%) of a component with a short relaxation time (S component)
• T _2s : T ₂ relaxation time (ms) of the S component
• β: Proton fraction (%) of a component with a long relaxation time (L component)
• T _2L : T ₂ relaxation time (ms) of the L component
• t: examination time (ms)
• Wa: form factor (= 1)

The measurement conditions in the above measurement are as described below. • 90° pulse width: 2.1µs • Repeat time: 1s • Number of Samples: 32 times • Measuring temperature: 30℃

(2) Amount of sinking measured with a TMA in an environment at 23°C

The amount of sinking of a first pressure-sensitive adhesive layer was measured with a TMA Q400 (manufactured by TA Instruments) under the following conditions: the probe of the TMA Q400 was caused to penetrate the layer; the nitrogen gas flow rate was 50.0 ml/min; the indentation load was 0.01 N; the temperature of the measuring atmosphere was 23.0 °C; and the indentation load time was 60 minutes. The number N of performing the measurement was set to 5, and the average of 3 measured values excluding the maximum and the minimum of these N measured values was used as the amount of sinking of the sample.

(3) Change in thickness by dropping 4-tert-butylphenyl glycidyl ether

A given amount (0.02 g when a 22 mm diameter syringe was used) of 4-tert-butylphenyl glycidyl ether was dropped onto the surface of a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer was exposed in an environment of 23°C and 50% RH (RH) for 1 minute, after which the 4-tert-butylphenyl glycidyl ether was wiped off. The thickness change ratio ((Dt - It)/It) and the amount of thickness change (Dt - It) of the layer were determined by using the thickness (Dt) of the spot after wiping and the thickness (It) of the spot before dropping.

(4) Pressure sensitive adhesive strength (to PET)

A SUS304 sheet was bonded to the entirety of the surface of a pressure-sensitive adhesive sheet (measuring 20 mm wide by 140 mm long) opposite to its pressure-sensitive adhesive layer by means of a double-sided adhesive tape (manufactured by Nitto Denko Corporation, product name: "No. 531") with a 2 kg hand roller glued.

Next, a polyethylene terephthalate sheet (manufactured by Toray Industries, Inc., product name: "LUMIRROR S-10", thickness: 25 µm, width: 30 mm) was adhered to the entire surface of the pressure-sensitive adhesive layer (temperature: 23°C, humidity: 65%, one pass back and forth with a 2 kg roller).

An evaluation sample obtained in the manner described above was subjected to a tensile test. A product available under the product name "Shimadzu Autograph AG-120kN" from Shimadzu Corporation was used as the tensile tester. The evaluation sample was set in the tensile tester and was then allowed to stand at an ambient temperature of 23°C for 30 minutes from the start of the tensile test. The tensile test was performed under the conditions of a peel angle of 180° and a peel speed (pull speed) of 300 mm/min. A stress when the pressure-sensitive adhesive sheet peeled off from the PET film was measured, and the maximum stress at that time was used as the pressure-sensitive adhesive strength of the pressure-sensitive adhesive sheet.

(5) Pressure-sensitive adhesive strength (to the encapsulating resin)

A mold frame (mold size: a rectangle measuring 35 mm by 90 mm, thickness: 564 µm) was bonded to the first pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet (measuring 50 mm wide by 140 mm long) and a granular epoxy-based encapsulating material ( manufactured by Sumitomo Bakelite Co., Ltd., G730) was scattered into the mold frame such that the resin thickness after curing was 0.3 mm. Thereafter, the mold frame was covered with a silicone-treated release liner, and the encapsulating resin was molded with "HYDRAULIC FORMING MACHINE NS-VPF-50" manufactured by Meisho-press Co., Ltd. under the conditions of a temperature of 145°C, a molding time of 600 seconds, a pressurizing condition of 0.3 MPa (table size 300 mm square), an evacuation time of 600 seconds and a degree of vacuum of -0.1 MPa, thermoforming on the pressure-sensitive adhesive layer subjected.

Thereafter, the encapsulating resin was cured in an oven in a heating environment at 150°C for 7 hours. After the completion of the curing of the encapsulating resin, the sample was at 23°C and 50% relative humidity (RH) for 2 hours, and then a portion where the encapsulating resin and the first pressure-sensitive adhesive layer have been brought into contact with each other was cut into a size measuring 20 mm wide by 88 mm long .

An evaluation sample obtained in the manner described above was subjected to a tensile test. A product available under the product name "Shimadzu Autograph AG-120kN" from Shimadzu Corporation was used as the tensile tester. The evaluation sample was set in the tensile tester and was then allowed to stand at an ambient temperature of 23°C for 30 minutes, after which the tensile test was started. The tensile test was performed under the conditions of a peel angle of 180° and a peel speed (pull speed) of 300 mm/min. A stress at the time of peeling the pressure-sensitive adhesive sheet from the encapsulating resin was measured, and an average stress at that time was used as the pressure-sensitive adhesive strength of the pressure-sensitive adhesive sheet.

(6) Step between the semiconductor chip and the encapsulation resin

• Träger: Ein aus SUS hergestellter Träger mit einem Durchmesser von 220 mm
• Chip: Ein Si-Spiegelglanzchip mit den Abmessungen 7 mm lang mal 7 mm breit mal 400 µm dick
• Verbindungsvorrichtung: FC3000W (hergestellt von Toray Engineering Co., Ltd.)
• Verbindungsbedingungen: Wie nachstehend beschrieben
• Kompressionsverbindungszeit: 6 Sekunden
• Kompressionsverbindungsdruck: 10 N
• Kompressionsverbindungstemperatur: 23 °C
• Einkapselungseinrichtung: MS-150HP (hergestellt von Apic Yamada Corporation)
• Einkapselungsharz: G730 (hergestellt von Sumitomo Bakelite Co., Ltd.)
• Vorheizbedingungen: 130 °C × 30 Sekunden
• Zeitraum vom Vorheizen bis zum Beginn des Einkapselns: 1 Stunde
• Einkapselungstemperatur: 145 °C
• Evakuierungszeit: 5 Sekunden
• Einkapselungszeit: 600 Sekunden
• Klemmkraft: 3,6 MPa
• Einkapselungsdicke: 600 µm

An encapsulating step was performed on the pressure-sensitive adhesive surface of a pressure-sensitive adhesive tape under the following conditions, and the step height (distance) at an interface between a semiconductor chip (Si chip) and an encapsulating resin was measured.

• Beam: A beam made of SUS with a diameter of 220 mm
• Chip: A specular Si chip with dimensions 7 mm long by 7 mm wide by 400 µm thick
• Connecting device: FC3000W (manufactured by Toray Engineering Co., Ltd.)
• Connection Conditions: As described below
• Compression connection time: 6 seconds
• Compression connection pressure: 10 N
• Compression joint temperature: 23°C
• Encapsulation device: MS-150HP (manufactured by Apic Yamada Corporation)
• Encapsulating resin: G730 (manufactured by Sumitomo Bakelite Co., Ltd.)
• Preheating conditions: 130°C × 30 seconds
• Time from preheating to start of encapsulation: 1 hour
• Encapsulation temperature: 145°C
• Evacuation time: 5 seconds
• Encapsulation time: 600 seconds
• Clamping Force: 3.6Mpa
• Encapsulation thickness: 600 µm

• (1) Die Haftklebstofflage wurde mit dem SUS-Träger verbunden bzw. an diesen geklebt
  • Verbindungsbedingungen: In einer Atmosphäre bei 23 °C
  • Verbindungszylinderdruck: 0,1 MPa
  • Verbindungsgeschwindigkeit: 0,5 m/min

An encapsulation process was performed with the following procedure.

• (1) The pressure-sensitive adhesive sheet was adhered to the SUS carrier
  • Bonding Conditions: In an atmosphere at 23°C
  • Connecting cylinder pressure: 0.1Mpa
  • Connection speed: 0.5m/min

The surface of the pressure-sensitive adhesive layer to be bonded to the SUS carrier was the outer surface of a second pressure-sensitive adhesive layer.

• (2) Ein Si-Spiegelglanzchip wurde auf der Haftklebstoffschicht der Haftklebstofflage angeordnet, die mit der Verbindungsvorrichtung mit dem SUS-Träger verbunden worden ist.
• (3) Der SUS-Träger in einem Zustand, bei dem der Si-Spiegelglanzchip damit verbunden ist, wurde für einen vorgegebenen Zeitraum vorgeheizt.
• (4) Nach dem Vorheizen wurde die resultierende Anordnung in einer Umgebung bei 23 °C und 50 % relativer Feuchtigkeit (RH) für 1 Stunde stehengelassen und dann wurde das Einkapseln mit der vorgegebenen Einkapselungseinrichtung und dem vorgegebenen Harz bei den vorgegebenen Bedingungen durchgeführt. Der Einkapselungsvorgang wurde durch einheitliches Verteilen des Einkapselungsharzes auf dem SUS-Träger per Hand durchgeführt.
• (5) Das durch den Einkapselungsvorgang erhaltene Laminat wurde einem Aushärtungsvorgang zum Wärmeaushärten mit einem Ofen bei 150 °C für 4 Stunden unterzogen.
• (6) Das dem Wärmeaushärten unterzogene Laminat wurde in einer Umgebung bei 23 °C und 50 % relativer Feuchtigkeit (RH) für 5 Tage stehengelassen und dann wurde das Laminat auf einer Heizplatte derart erwärmt, dass der mit dem SUS-Träger verbundene Haftklebstoff aufschäumte und abgelöst wurde. Auf diese Weise wurde der SUS-Träger abgetrennt.
• (7) Das Haftklebstoffband wurde von dem Laminat nach dem Abtrennen des SUS-Trägers abgelöst. Auf diese Weise wurde ein eingekapselter Körper erhalten, der das Einkapselungsharz und den Si-Chip umfasst.
• (8) Eine Stufe an der Grenzfläche zwischen dem Si-Chip und dem Einkapselungsharz auf der Oberfläche des eingekapselten Körpers, der das Einkapselungsharz und den Si-Chip umfasst, dessen Oberfläche mit dem Haftklebstoff in Kontakt war, wurde mit einem Laserkonfokalmikroskop (OLS-4000, hergestellt von Olympus Corporation) gemessen, worauf die Stufenhöhe an der Grenzfläche zwischen dem Einkapselungsharz und dem Si-Chip gemessen wurde.

When the pressure-sensitive adhesive layer was a single-sided adhesive tape (devoid of the second pressure-sensitive adhesive layer), the SUS backing and the single-sided adhesive tape were bonded using a baseless pressure-sensitive adhesive layer 48 microns thick containing thermally expandable microspheres and bonded using a silicone A release liner comprising a PET film having a thickness of 38 µm (MRF38, manufactured by Mitsubishi Chemical Corporation) and a silicone release liner comprising a PET film having a thickness of 75 µm (PET-75-SCA0, manufactured by Fujiko Co., Ltd.) was fixed to each other, and evaluation was conducted.

• (2) A mirror-like Si chip was placed on the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet bonded to the SUS substrate with the bonding jig.
• (3) The SUS substrate in a state where the specular Si chip is bonded thereto was preheated for a predetermined period of time.
• (4) After preheating, the resultant assembly was allowed to stand in an environment of 23°C and 50% RH for 1 hour, and then encapsulation was performed with the specified encapsulant and resin under the specified conditions. The encapsulation process was performed by spreading the encapsulation resin uniformly on the SUS carrier by hand.
• (5) The laminate obtained through the encapsulation process was subjected to a curing process for thermosetting with an oven at 150°C for 4 hours.
• (6) The laminate subjected to thermosetting was allowed to stand in an environment at 23°C and 50% relative humidity (RH) for 5 days, and then the laminate was heated on a hot plate such that the pressure-sensitive adhesive bonded to the SUS carrier foamed and was replaced. In this way, the SUS carrier was separated.
• (7) The pressure-sensitive adhesive tape was peeled off the laminate after separating the SUS backing. In this way, an encapsulated body comprising the encapsulating resin and the Si chip was obtained.
• (8) A step at the interface between the Si chip and the encapsulating resin on the surface of the encapsulated body comprising the encapsulating resin and the Si chip whose surface was in contact with the pressure-sensitive adhesive was observed with a laser confocal microscope (OLS-4000 , manufactured by Olympus Corporation), and then the step height at the interface between the encapsulating resin and the Si chip was measured.

[Example 1]

100 parts by weight of an acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, 2-ethylhexyl acrylate constituent unit:acrylic acid constituent unit = 95:5 (weight ratio)), 5 parts by weight of an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., Product name: "TETRAD-C") and 100 parts by weight of toluene were mixed to prepare a composition for forming a pressure-sensitive adhesive layer.

The composition for forming a pressure-sensitive adhesive layer was applied onto a surface of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: "LUMIRROR S10", thickness: 38 µm) serving as a base material to provide a pressure-sensitive adhesive sheet (1) which Base material and a first pressure-sensitive adhesive layer (thickness: 10 microns).

100 parts by weight of an acrylic copolymer C (a copolymer of 2-ethylhexyl acrylate, ethyl acrylate, methyl methacrylate and 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate constituent unit: ethyl acrylate constituent unit: methyl methacrylate constituent unit: 2-hydroxyethyl acrylate constituent unit = 30:70:5:4 (weight ratio )), 30 parts by weight of thermally expandable microbeads (manufactured by Matsumoto Yushi-Seiyaku Co., Ltd., product name: "MATSUMOTO MICROSPHERE F-190D"), 1.4 parts by weight of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name: "CORONATE L"), 10 parts by weight of a tackifier (manufactured by Yasuhara Chemical Co., Ltd., product name: "MIGHTY ACE G125") and 100 parts by weight of toluene were mixed to prepare a composition for forming a pressure-sensitive adhesive layer. The composition was applied onto the surface of the polyethylene terephthalate film of the pressure-sensitive adhesive sheet (1) opposite to the first pressure-sensitive adhesive layer to form a second pressure-sensitive adhesive layer (thickness: 45 µm). A double-sided pressure-sensitive adhesive sheet was obtained in this way.

[Example 2]

100 parts by weight of acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, 2-ethylhexyl acrylate constituent unit:acrylic acid constituent unit = 95:5 (weight ratio)), 5 parts by weight of an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., product name: "TETRAD-C"), 10 parts by weight of a tackifier (manufactured by Yasuhara Chemical Co., Ltd., product name: "MIGHTY ACE G125") and 100 parts by weight of toluene were mixed to prepare a composition for forming a pressure-sensitive adhesive layer.

The composition for forming a pressure-sensitive adhesive layer was applied onto one surface of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: "LUMIRROR S10", thickness: 38 µm) serving as a base material to provide a pressure-sensitive adhesive sheet (2). which comprises the base material and a first pressure-sensitive adhesive layer (thickness: 10 µm).

A second pressure-sensitive adhesive layer was formed on the surface of the polyethylene terephthalate film of pressure-sensitive adhesive sheet (2) opposite to the first pressure-sensitive adhesive layer in the same manner as in Example 1. A double-sided pressure-sensitive adhesive sheet was obtained in this way.

[Example 3]

100 parts by weight of an acrylic copolymer B (a copolymer of ethyl acrylate, butyl acrylate, acrylic acid and 2-hydroxyethyl acrylate, ethyl acrylate constituent unit:butyl acrylate constituent unit:acrylic acid constituent unit:2-hydroxyethyl acrylate constituent unit=50:50:5:0.1 (weight ratio)) , 5 parts by weight of an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., product name: "TETRAD-C"), 10 parts by weight of a tackifier (manufactured by Yasuhara Chemical Co., Ltd., product name: "MIGHTY ACE G125") and 100 parts by weight of toluene were mixed to prepare a composition for forming a pressure-sensitive adhesive layer.

The composition for forming a pressure-sensitive adhesive layer was applied onto one surface of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: "LUMIRROR S10", thickness: 38 µm) serving as a base material to provide a pressure-sensitive adhesive sheet (3). which comprises the base material and a first pressure-sensitive adhesive layer (thickness: 10 µm).

A second pressure-sensitive adhesive layer was formed on the surface of the polyethylene terephthalate film of pressure-sensitive adhesive sheet (3) opposite to the first pressure-sensitive adhesive layer in the same manner as in Example 1. A double-sided pressure-sensitive adhesive sheet was obtained in this way.

[Example 4]

A double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 2 except that a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: "LUMIRROR S10", thickness: 100 µm) was used as the base material.

[Comparative Example 1]

100 parts by weight of the acrylic copolymer C (a copolymer of 2-ethylhexyl acrylate, ethyl acrylate, methyl methacrylate and 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate constituent unit: ethyl acrylate constituent unit: methyl methacrylate constituent unit: 2-hydroxyethyl acrylate constituent unit = 30:70:5:4 (weight ratio )), 1.5 parts by weight of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name: "CORONATE L"), 5 parts by weight of a tackifier (manufactured by Yasuhara Chemical Co., Ltd., product name: "MIGHTY ACE G125") and 100 parts by weight of toluene were mixed to prepare a composition for forming a pressure-sensitive adhesive layer.

The composition for forming a pressure-sensitive adhesive layer was applied onto one surface of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: "LUMIRROR S10", thickness: 38 µm) serving as a base material to provide a pressure-sensitive adhesive sheet (4). which comprises the base material and a pressure-sensitive adhesive layer (thickness: 10 µm).

A second pressure-sensitive adhesive layer was formed on the surface of the polyethylene terephthalate film of pressure-sensitive adhesive sheet (4) opposite to the first pressure-sensitive adhesive layer in the same manner as in Example 1. A double-sided pressure-sensitive adhesive sheet was obtained in this way.

[Comparative Example 2]

100 parts by weight of an acrylic copolymer D (a copolymer of 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate constituent unit:2-hydroxyethyl acrylate constituent unit = 100:4 (weight ratio)), 1.5 parts by weight of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name: "CORONATE L") and 100 parts by weight of toluene were mixed to prepare a composition for forming a pressure-sensitive adhesive layer.

The composition for forming a pressure-sensitive adhesive layer was applied onto one surface of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: "LUMIRROR S10", thickness: 38 µm) serving as a base material to provide a pressure-sensitive adhesive sheet (5). which comprises the base material and a pressure-sensitive adhesive layer (thickness: 10 µm).

A second pressure-sensitive adhesive layer was formed on the surface of the polyethylene terephthalate film of pressure-sensitive adhesive sheet (5) opposite to the first pressure-sensitive adhesive layer in the same manner as in Example 1. A double-sided pressure-sensitive adhesive sheet was obtained in this way. Table 1 example 1 example 2 Example 3 example 4 Comparative example 1 Comparative example 2 Blending Amount of Pressure-Sensitive Adhesive Composition Component to Form First Pressure-Sensitive Adhesive Layer (part(s) by weight) prepolymer Polymer A (2EHA/AA = 95/5) 100 100 100 Polymer B (EA/BA/AA/HEA = 50/50/5/0.1) 100 Polymer C (2EHA/EA/MMA/HEA = 30/70/5/4) 100 Polymer D (2EHA/HEA = 100/4) 100 crosslinking agent CORONATE L (isocyanate-based crosslinking agent) 1.5 1.5 TETRAD-C (epoxy-based crosslinking agent) 5 5 5 5 tackifier 10 10 10 5 Thickness of the adhesive layer [µm] 10 10 10 10 10 10 Thickness of the base material [µm] 38 38 38 100 38 38 Evaluation Thickness of the pressure-sensitive adhesive layer before dropping 4-t-butylphenyl glycidyl ether [µm] 10 10 10 10 10 10 Thickness of the pressure-sensitive adhesive layer after dropping 4-t-butylphenyl glycidyl ether [µm] 16 16 18 16 11 33 Amount of change in thickness of the pressure-sensitive adhesive layer [µm] 6 6 8th 6 1 23 Pressure-sensitive adhesive layer thickness change ratio 60% 60% 80% 60% 10% 230% T ₂ obtained by pulse NMR (S component) [µs] 28 28 25 28 52 61 sp value of main polymer [J/cm ³ ]^1/2] 19.3 19.3 19.6 19.3 20.7 19.1 Pressure-sensitive adhesive strength on the resin [N/20 mm] 0.6 1.1 10 0.5 19 2.4 Pressure-sensitive adhesive strength on PET [N/20 mm] 0.12 0.23 0.52 0.23 4.73 4.6 Amount of sinking [µm], measured by TMA in an environment at 23 °C 1.8 2 1.1 2 3.1 4 Amount of sinking [µm], measured by TMA in an environment at 145 °C 34 34 34 15 33 35 Step height at the interface between the encapsulation resin and the Si chip [µm] 2.4 2.6 1.9 2.6 3.6 3.1

Reference List

10

base material

20

pressure-sensitive adhesive layer

30

Second pressure-sensitive adhesive layer

100, 200

pressure-sensitive adhesive layer

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• JP2001308116A [0003]
• JP2001313350A [0003]
• JP 2018009050 A [0072]

Claims (14)

A pressure-sensitive adhesive sheet comprising: a base material; and a pressure-sensitive adhesive layer disposed on at least one side of the base material, the pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive layer having an amount of sink of 5 µm or less measured with a TMA in an environment at 23 °C, and wherein an S component obtained by pulse NMR of the pressure-sensitive adhesive layer has a T ₂ relaxation time (T _2s ) of 45 µs or less. pressure-sensitive adhesive layer claim 1 , wherein after dropping 4-tert-butylphenyl glycidyl ether onto a surface of the pressure-sensitive adhesive layer and allowing the pressure-sensitive adhesive layer to stand for 1 minute, the thickness of the pressure-sensitive adhesive layer changes at a ratio of 160% or less. pressure-sensitive adhesive layer claim 1 or 2 , wherein after dropping 4-tert-butylphenyl glycidyl ether onto a surface of the pressure-sensitive adhesive layer and allowing the pressure-sensitive adhesive layer to stand for 1 minute, the thickness of the pressure-sensitive adhesive layer changes to an extent of 20 µm or less. Pressure-sensitive adhesive layer according to one of Claims 1 until 3 wherein the pressure-sensitive adhesive layer contains a pressure-sensitive adhesive, and wherein the pressure-sensitive adhesive contains a base polymer having an sp value of from 18 (cal/cm ³ ) ^1/2 to 20 (cal/cm ³ ) ^1/2 . Pressure-sensitive adhesive layer according to one of Claims 1 until 4 , wherein the acrylic pressure-sensitive adhesive contains a crosslinked base material made of an acrylic polymer as the base polymer. Pressure-sensitive adhesive layer according to one of Claims 1 until 5 wherein the acrylic pressure-sensitive adhesive contains an epoxy-based crosslinking agent. pressure-sensitive adhesive layer claim 6 wherein the epoxy-based crosslinking agent is blended in an amount of 0.6 parts by weight to 15 parts by weight based on 100 parts by weight of the acrylic polymer. Pressure-sensitive adhesive layer according to one of Claims 1 until 7 , wherein the base material is a resin sheet comprising a resin having a glass transition temperature (Tg) of 25°C or more. Pressure-sensitive adhesive layer according to one of Claims 1 until 8th , wherein the thickness of the base material makes up from 20% to 90% of the total thickness of the pressure-sensitive adhesive layer. Pressure-sensitive adhesive layer according to one of Claims 1 until 9 , wherein the pressure-sensitive adhesive layer has an amount of sink of 1 µm to 35 µm as measured by the TMA in a 145°C environment. Pressure-sensitive adhesive layer according to one of Claims 1 until 10 wherein the pressure-sensitive adhesive layer generates nitrogen gas in an amount of from 0.06% to 1.0% by weight when subjected to a heat treatment. Pressure-sensitive adhesive layer according to one of Claims 1 until 11 wherein the pressure-sensitive adhesive layer comprises: the base material; the pressure-sensitive adhesive layer disposed on one side of the base material; and a second pressure-sensitive adhesive layer disposed on a side of the base material opposite to the pressure-sensitive adhesive layer. Pressure-sensitive adhesive layer according to one of Claims 1 until 12 wherein the pressure sensitive adhesive layer is a temporary fixing material used in a step of encapsulating a semiconductor chip in a resin. pressure-sensitive adhesive layer Claim 13 wherein the pressure-sensitive adhesive layer is used when the encapsulating resin is cured on the pressure-sensitive adhesive layer.

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